1. Field of the Invention
The present invention relates to a metadata collecting device, a method therefore and a computer readable medium storing a program for performing the method, for efficiently collecting and accumulating, for example, metadata of content, and for effectively updating the accumulated (cached) metadata.
2. Related Art
In recent years, in the context of the spread of broadband, multimedia-content distribution services using IP (Internet Protocol) communication are operated by various communication service providers. Provided are a wide variety of services ranging from a low-resolution video distribution service for a mobile phone to a high-resolution video distribution service having HD (High Definition) quality for a digital television.
The multimedia-content distribution services include a VoD (Video on Demand) video distribution service in which videos are distributed in unicast. This service is roughly classified into two types of that using a portable service and that using ECG (Electronic Content Guide), as a navigation of search/selection of content.
The portal service is a service for performing the navigation on a WEB browser provided by a service provider. A user accesses to the WEB page called “Portal” provided by the respective service providers to search/select desired content, and then, receive video streams. In the portal service, a content search or the like are all performed on a server, and its result is presented to the user on the WEB page.
On the other hand, ECG is an application on a receiving device, and obtains program information called as metadata and selects desired one among a certain number of metadata, and then, provides to the user an interface for search, display, selection, view, and purchase. A service using ECG takes a configuration in which the metadata becoming a key part needed for the navigation has been previously accumulated on the receiving device, and is used. The service using ECG, thus, has an advantage to operate at a high speed, compared with the portal service required to obtain also screen structure information on a site including image information. Moreover, the service using ECG has also an advantage or the like that a receiver side can determine a screen design; operation or a screen transition using a receiver remote control, which cannot be realized by a browser, is enabled etc. Further, in the service using ECG, it is possible to realize a multiservice navigation by collecting metadata from a plurality of services, merging those metadata, and then, presenting the metadata to the user. Examples for realizing this multiservice navigation include a technology disclosed in JP-A 2004-102767 (Kokai).
In JP-A 2004-102767 (Kokai), a metadata collecting device has previously collected and cached metadata from a plurality of metadata providing devices, and when a receiving device requests for metadata obtainment to the metadata collecting device, the metadata held by these metadata providing devices is returned to the receiving device in a unified format.
In JP-A 2004-102767 (Kokai), in a case where it is necessary to update the metadata requested by the receiving device, in other words, a case where there is a discrepancy between the cached metadata and the metadata retained by the metadata providing device, it is required to obtain the metadata from the metadata providing device again. Therefore, a service in which the metadata are frequently updated has a problem that a hit rate by cache becomes low, and accordingly, this gives rise to a need for collecting the metadata from the metadata providing device again, thereby requiring time until content are displayed on the receiving device.
Additionally, in JP-A 2004-102767 (Kokai), supposed is a configuration in which the metadata collecting device is arranged on a server side, so that it is not possible to make content accumulated in a home HDD recorder be a search object. Further, all of the metadata are obtained from the metadata collecting device, so that it is not possible to adapt the technology to a consumer device such as a digital television having a large restriction in capacity or the like of a hard disk, a memory.
As stated above, in a case where the number of content provided by the service is extremely large, it is difficult to apply caching of all the content to the consumer device such as the digital television having a large restriction in capacity or the like of the hard disk, the memory. Additionally, the service in which content are frequently updated faces also a problem that a cache hit rate becomes low, thereby giving rise to the need for obtaining the metadata from the metadata providing device again, and accordingly, spoiling light operational feeling.